Loans - Changes in Accretable Yield on Acquired Loans (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield, beginning balance	$ 6,420	$ 6,208
Accretion recognized in earnings	(1,042)	(1,182)
Reclassifications from nonaccretable difference for loans with improving cash flows	214	1,005
Increases (reductions) in accretable yield for non-credit related changes in expected cash flows	(939)	389
Accretable yield, ending balance	4,653	6,420
Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield, beginning balance	2,114	1,899
Accretion recognized in earnings	(379)	(427)
Reclassifications from nonaccretable difference for loans with improving cash flows	94	629
Increases (reductions) in accretable yield for non-credit related changes in expected cash flows	(344)	13
Accretable yield, ending balance	1,485	2,114
Non-Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield, beginning balance	4,306	4,309
Accretion recognized in earnings	(663)	(755)
Reclassifications from nonaccretable difference for loans with improving cash flows	120	376
Increases (reductions) in accretable yield for non-credit related changes in expected cash flows	(595)	376
Accretable yield, ending balance	$ 3,168	$ 4,306

Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Increase (Decrease) Due to Non-Credit Related Changes in Expected Cash Flows

No definition available.

+ Details

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- Definition

Amount of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 15

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

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- Definition

Amount of decrease from accretion of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

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- Definition

Amount of increase of reclassification from nonaccretable difference to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

+ Details

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